Studies will continue on our 2B8 clonal cell line which was derived from normal fetal anterior pituitary cells. In culture, the 2B8 cells produce only prolactin (insofar as we can determine by radioimmunoassay) and we have examine the direct effects of a number of regulatory agents such as steroids, hypothalamic hormones, dopamine and prolactin itself on prolactin secretion by these clonal cells. During the coming year we will carry out a series of experiments in which 2B8 clonal cells will be implanted into immature, hypophysectomized rats. Different implantation sites will be employed. We want to determine if the prolactin secreted by these cells is biologically active in the rat. We also will study the morphology of the grafted cells at varying time intervals after implantation to determine if they survive and continue to secrete prolactin. We are concerned about the possibility of the grafted cells inducing an immunological rejection response or perhaps forming tumors. We have recently discovered that some of our 2B8 cells have a hyperdiploid karyotype, so we will study the karyotype of the cells before implantation, and after implantation and return to culture. A major objective of these studies will be to determine if our 2B8 clonal cells behave as normal cells when returned to the environment of immature, hypophysectomized rat.